I’m assuming chickenkiller.com is a hosting service that gives you something.chickenkiller.com domain names? It appears a great many certificates have been issued recently for chickenkiller.com: https://crt.sh/?q=%chickenkiller.com
There’s a rate limit of 20/week per domain, and while renewals are not blocked by this limit, they do count against it. You can keep trying a few time a day in the hopes that you get lucky, but a better option would be to contact whoever runs chickenkiller.com and recommend they do one of the following:
- Submit their site to the Public Suffix List, which will both prevent the base domain form encountering rate limits, but also increase the security of sites hosted there by preventing cross-domain cookies. They’r not very keen on adding domains to this list solely to avoid Let’s Encrypt rate limits, but it sounds like there are valid reasons to have it placed here.
- Alternatively, the owners of
chickenkiller.comcould apply to Let’s Encrypt for a rate limit exemption; see the Overrides section on the rate limits page.
Alternatively, you could change providers and get your own domain name that doesn’t suffer from this issue.
EDIT: Counting up certificates issued for this domain, as long as nobody renews theirs in the meantime, you should be able to issue in several hours. Once you get lucky and manage to issue a certificate, you can keep renewing it in the future without having to worry about this particular rate limit.